The overall question addressed in this grant application regards the mechanisms by which cytokine genes are activated in human alveolar macrophages (AM) during sepsis-induced acute lung injury. Endotoxin (LPS) is released during sepsis and is a potent trigger for cytokine production by macrophages, in vivo and in vitro. The importance of this is illustrated by the observations that cytokines are released during sepsis and that inhibition of cytokines prevents acute lung injury during sepsis in animal models of the disease. Studies have shown that the p38 mitogen activated protein kinase (MAPK) pathway is essential for release of cytokines by monocytes in response to endotoxin. No studies, however, have defined a role for other MAPK pathways in release of cytokines in response to LPS. The focus of this application is to define the role(s) of the p42/44 MAPK pathway and its interaction with the p38 MAPK pathway in regulating cytokine gene expression in human AM in response to LPS. In these studies, the applicant explores the novel observation that both the p42/44 and p38 MAPK pathways are required for optimal cytokine gene expression in human AM in response to LPS and that each of these MAPK pathways has a different effect on cytokine gene expression. More emphasis is placed on studies relating to the p42/44 kinase pathway since the relationship of this pathway to LPS-induced cytokine gene expression is less well-defined. The applicant also explores the novel observations that activation of both an oxidant signal and a phosphatidylcholine-specific phospholipase C (PC-PLC) regulate activation of the p42/44 MAPK pathway and cytokine gene expression. These observations form the basis for studies in Aim 1. In Aim 2, he explores novel studies that relate activation of these MAPK pathways to the generation of active transcription factors that regulate cytokine gene expression. Although the studies in this application relate, directly, to sepsis-induced acute lung injury, they are novel in that they also provide important basic clues to understand macrophage cytokine gene regulation.